Antennas for monopulse radar systems having planar slot array and coupling means for providing sum and difference signals



Nov. 23, 1965 1 THOUREL 3220,007 I I ANTENNAS FOR MONOPULSE RADAR SYSTEMS HAVING PLANAR SLOT ARRAY AND GOUPLING MEANS FOR PROVIDING SUM AND DIFFERENCE SIGNALS Filed March 14, 1962 ELEVATION DIFFERENCE SIGNAL A AZIMUTH DIFFERENCE SIGNAL G United States Patent O M 3,220,007 ANTENNAS FOR MONOPULSE RADAR SYSTEMS HAVING PLANAR SLOT ARRAY AND COU PLING MEANS FOR PROVIDING SUM AND DIFFERENCE SIGNALS Lo Thourel, Paris, `France, assigner to @SFr-Compagnie Generale de Teiegraphie Sans Fil, a corporation of France Filed Mar. 14, 1962, Ser. No. 179,665 Claims priority, application France, Mar. 1'7, 1961,

p 855,958 6 Claims. (ci. 34a- 771) The present invention relates to radar antennas. More particularly, it is an object of the invention to provide an antenna adapted to radiate a plurality of electromagnetic-wave beams.

An antenna according to the invention comprises an arrangement of slotted waveguides extending in parallel relationship in the same plane and arranged in successive pairs. The waveguides of each one of said pairs radiate, respectively, along two predetermined directions.

Means are associated with said pairs of waveguides, for receiving the sum of the signals collected by each pair and the difference of these signals.

The difference signals produced by each pair feed in phase a rst retlector, in the focus of which is placed a horn collecting the sum of these signals and providing the elevation error signal.

The sum signals produced by each pair feed in phase a second reflector, in the focus of which are two horns connected to a magic-T, the sumechannel of which provides the reference signal While the difference-channel provides the bearing error signal.

The invention will be best understood from the following description and appended drawings, wherein:

FIG. lA is a perspective view of an antenna according to the invention;

FIGS. 2 and 3 are respectively cross-sections through the plane of symmetry and the plane comprising the waveguides assembly of the radiating pattern of the antenna.

The antenna according to the invention shown in FIG. l comprises an assernbly of slotted waveguides l and 2, in parallel relationship, guides 1 and 2 contacting one another along their small sides.

These waveguides are formed with transversal slots 3. Of course, other types of slots or other radiating sources may be used, without departing from the scope of the invention. The guides of each pair are connected by a two hole directional coupler 4, provided in their common wall, and, in addition, guide 2 comprises a phase-Shifter 5 adapted to provide a 1r/2 phase-shift. Accordingly, the vector-sum and the vector-difference of the signals picked up by guides l and 2 are respectively collected at points E and D of said guides.

The slots having the same position in guides l and 2 are fed in phase by the collected signal, the spacing between the slots being the same in all the guides.

Taking the trihedral Oxyz as the reference trihedral, with Oz perpendicular to the plane Oxy comprising guides 1 and 2, and Ox coinciding with the direction of energy propagation in the guides, the assembly of guides 1 and the assembly of guides 2 have radiation patterns 1 and 2' which are symmetrical with respect to Ox, as shown in FIG. 4.

Means known per se are provided to cause the phase velocity in guides 1 and 2 to be diiierent. This results in guides 1 having a maximum radiation in a direction A1 of plane zOx, whereas guides 2 have a maximum radiation in a direction A2 of the same plane.

Transition elements 6 connect the outputs D of guides 3,220,007 Patented Nov. 23, 1965 ICC 2 to a first reflector '7, for example of the parabolic type. Points 2 are connected by transition elements 8 to a second reflector 99. Reilectors 7 and 9 may, for example, be located .below the plane of guides, in parallel relationship thereto. The operation is as` follows. The energy coming from guide 2, FIGURE 2, is phaseshifted by 1r/2 by phaseshifter 5, and divided in two equal parts; one owing directly to D, the other, through coupler 4, to E; this latter part is phases-hifted -fby said coupler and has consequently a total phaseshift or 1r.

As to the energy coming from guide 1;, the part llowing directly to E has no phaseshift and is algebraically added to the energy coming from guide 2. Since this latter has been phaseshifted by 1r in passing through coupier 4, this algebraical addition is in fact arithmetical subtraction. The other part flowing from guide l to point D, through coupler d, is in turn phaseshifted by r/ 2, and consequently at point D, is in phase with the energy coming from guide 2. Consequently there is a summation at point D.

In the focus of reflector 7, there is located a first horn '71 which sums up the vectorial difference to provide signals I.

FIGS. 2 and 3 show that the assembly operates as a monopulse antenna, the pointing direction of which is contained in the plane Ox and is the bisectrix D of the angle forme-d by directions A1 and A2. When the target leaves this axis, while remaining in the plane zOx (error in elevation), the difference signals will appear and are summed up in reflector 7 by horn 71 which; receives the sum of all these signals. This provides, after detection, an elevation error signal A, this signal being equal to zero, when the target is in the pointing direction and appearing, when the target leaves this direction, while remaining in the zOx plane, is in fact the elevation error signal.

Signals E are summed up by means of reflector 9 in the focal plane of which there are horns and 91, as shown in FIGS. 5 and 6. These two horns are coupled to the two input branches of a magic-T 92'.

On one of the output branches of the T, there is collected the signal S, or the reference sum signal of the monopulse radar.

The second output branch provides the dilerence of the signals respectively received by horns 90 and 91. This difference is nil when the target is in the direction Ox. Accordingly, this signal is the signal indicating the error in bearing of the monopulse radar.

Of course the invention is not limited to the one embodiment described and shown which has been given solely by way of example.

What is claimed is:

t. An antenna for ultra-high frequency energy comprising: a plurality of waveguides extending in the same plane in parallel relationship to one another and arranged in successive pairs, each guide having radiating discontinuities equispa'ced along said guide; means associated with each pair of said guides for receiving the sum of the signals collected by the two guides of said pair and the diiference of said signals; and parabolic reflector means for summing the respective sum signals of said pairs and the respective difference signals thereof.

2. An antenna for ultra-high frequency energy comprising: a plurality of rectangular waveguides extending in the same plane in parallel relationship to one another having respective large and small walls and arranged in successive pairs, the guides of each pair contacting one another along their respective small walls; each of said guides having equispaced radiating slots in their large walls, said guides being arranged to form a continuous hat assembly; means associated with each pair of said guides for receiving the snm of the signals collected by the two guides of said pair and the difference of said signals; and parabolic reflector means for summing the respective sum signals of said pairs and the respective difference signals thereof.

3. An antenna for ultraehigh frequency energy cornprising: a plurality of rectangular waveguides extending in the same plane in parallel relationship to one another and having respective large and small walls, said large walls forming a continuous at surface, said guides being arranged in successive pairs, each of said guides having radiating equidistant slots in one of their large walls; the respective guides of each pair radiating respectively along two predetermined directions; means associated with eac-h pair of guides for obtaining the sum of the signals collected by the guides of said pair and the difference of said signals; parabolic reflector means for summing up the respective sum signals and the respective difference signals of said pairs for providing a reference signal, an elevation error signal and a bearing. error signal.

4. An antenna for ultra-high frequency energy comprising: a plurality of rectangular waveguides extending in the same plane in parallel relationship to one another and having respective large and small walls, said large walls forming a continuous llat surface, said guides being arranged in successive pairs, each of said guides having radiating equidistant slots in one of their large walls; the guides of each pair radiating respectively along two predetermined directions; means associated with each pair of guides for obtaining the sum of the signals collected by the guides of said pair and the difference of said signals; a first and a second parabolic reector respectively coupled to said guides, for respectively surnming up the respective sum signals and the respective difference signals from said pairs for providing a ref erence signal, an elevation error signal and a bearing error signal.

5. An antenna for ultra-high frequency energy cornprising: a plurality of rectangular waveguides extending in the same plane in parallel relationship to one another and having respective large and small walls, said large walls forming a continuous flat surface, said guides being arranged in successive pairs, each of said guides having radiating equidistant slots in one of their large walls;

the guides of each pair radiating respectively along two predetermined directions; means associated with each pair of guides for obtaining the sum of the signals collected by the guides of said pair and the difference of said signals; a first and a second parabolic reflector respectively coupled to said guides; a rst horn in the focal plane of said rst reflector for summing up the respective sum signals of said pairs and providing a reference signal; a second and a third =horn in the focal plane of said second reector, and coupling means between said horns, said means having two outputs, for respectively providing an elevation error signal and a bearing error signal.

6. An antenna for ultra-high frequency energy comprising: a plurality of rectangular waveguides extending in the same plane in parallel relationship to one another and having respective large and small walls, said large walls forming a continuous flat surface, said guides being arranged in successive pairs, each of said guides having radiating equidistant slots in one of their large walls; the guides of each pair radiating respectively along two predetermined directions; means associated with each pair of guides for obtaining the sum of the signals collected by the guides of said pair and the difference of said signals; a rst and a second parabolic reflector respectively coupled to said guides; a first horn in the focal plane of said rst reector for summing up the respective sum signals of said pairs and providing a Ireference signal; a second and a third horn in the focal plane of said second rellector, a coupler having two inputs respectively connected to said second and said third horns and two outputs for respectively providing an elevation error signal and a bearing error signal.

References Cited by the Examiner UNITED STATES PATENTS 2,567,197 9/1951 FOX 343--16 2,810,908 10/1957 Crawford 343-786 2,940,075 6/1960 Stavis 343-777 2,967,301 l/l96l Rearwin 343--777 2,981,948 4/1961 Kurtz 343-l6.1

HERMAN KARL SAALBACH, Primary Examiner. 

1. AN ANTENNA FOR ULTRA-HIGH FREQUENCY ENERGY COMPRISING: A PLURALITY OF WAVEGUIDES EXTENDING IN THE SAME PLANE IN PARALLEL RELATIONSHIP TO ONE ANOTHER AND ARRANGED IN SUCCESSIVE PAIRS, EACH GUIDE HAVING RADIATING DISCONTINUITIES EQUISPACED ALONG SAID GUIDE; MEANS ASSOCIATED WITH EACH PAIR OF SAID GUIDES FOR RECEIVING THE SUM OF THE SIGNALS COLLECTED BY THE TWO GUIDES OF SAID PAIR AND THE DIFFERENCE OF SAID SIGNALS; AND PARABOLIC REFLECTOR MEANS FOR SUMMING THE RESPECTIVE SUM SIGNALS OF SAID PAIRS AND THE RESPECTIVE DIFFERENCE SIGNALS THEREOF. 